using System;

using System.Query;

using Danielfe;


class Program

{

    static void Main(string[] args)

    {

        string[] aBunchOfWords = {"One","Two", "Hello", 

  "World", "Four", "Five"};


        var result =    

            from s in aBunchOfWords // query the string array 

            where s.Length == 5     // for all words with length = 5

            select s;               // and return the string


        //PrintToConsole is an Extension method that prints the value

        result.Print();

    }

 }

y para que lo vean como funcionaría con un SQL Server, va un ejemplo, y me parece que no hace falta explicarlo

using System;

using System.Query;

using Danielfe;

using System.Data.DLinq; //DLinq is LINQ for Databases

using nwind; //Custom namespace that is tool generated 


class Program

{

    static void Main(string[] args)

    {

        Northwind db = new Northwind("Data Source=(local);Initial Catalog=Northwind;Integrated Security=True");   

        TableCustomers> allCustomers = db.GetTableCustomers>();


        var result = 

                from c in allCustomers

                where c.ContactTitle.Length == 5

                select c.ContactName;


        result.Print();   

    }

 }

Proyecto LINQ